Acoustic Inspection of Coated Steel Bar in Reinforced Concrete Structure

Bridges with reinforeerneut corrosion problems are now under careful inspection in Taiwan. Costly maintenance programs are underway and raising S"erious safety concem. There are various engineering solutions to salt-induced corrosion. Among them epoxycoated reinforcing bars, commonly referred to as rebar, are frequently used in marine environment and other areas due to its durability, reasonable cost, and convenience. However, coated rebar has lower bond strength and is less ductile than uncoated rebar. Thus it could result in larger crack width during pull-out tests [1,2]. The bond strength between coated steel bars and covered concrete results from the adhesion at the steel-concrete boundary, the frictional force, and the interlocking force provided by the raised ribs at the steel bar surface. The interlocking force is much stronger than the other two, while the frictional force occurs only if the adhesion vanishes after delamination or disbonding starts.